Investigators are refusing to say how they know gunshots sparked a wildfire that destroyed dozens of homes near Yosemite National Park.

California Department of Forestry and Fire Protection Battalion Chief Mike Mohler on Tuesday cited an ongoing investigation that he says keeps him from revealing details.

The fire started mid-July in the rugged Sierra Nevada foothills of Central California. It destroyed 63 homes.

Flames drove thousands of residents out of small communities such as Mariposa, a popular stopover for tourists headed to nearby Yosemite.

Mohler is asking the public to report seeing any vehicles or anything unusual to help investigators piece together the case.

He says shooting is allowed on public land where the fire started.

Investigators are offering a $2,000 reward for information leading to a conviction.